A jewel was a type of stone.
Eumachia believed Melanie Bush and the Seventh Doctor were only pretending to be messengers from Isis, and framed Mel for stealing some jewels to discredit the goddess. (AUDIO: The Fires of Vulcan)
Pelisipodron was a planet of jewels visited by the Seventh Doctor and Ace. (AUDIO: Revenge of the Swarm)
Ada Mullins was secretly the jewel thief known as "the Unicorn" in 1920s England. (TV: The Unicorn and the Wasp)